1. Field of the Invention
This invention relates to upright keyboard instruments such as electronic upright pianos that realize real key-touch feelings (or key-touch sensations) in depressing and releasing keys.
2. Description of the Related Art
In general, electronic upright pianos comprise hammers that are rotatably moved to strike strings upon depressions of keys, and actions (or action mechanisms) for transmitting movements of depressed keys to hammers, wherein movements of keys are detected by sensors to produce detection results, based on which musical tones are correspondingly produced. Therefore, players (or users) are able to play electronic upright pianos with key-touch feelings (e.g., key-touch sensations, key-touch responses and reactions, or resistances of keys being depressed) similar to those of acoustic upright pianos, while they are able to listen to sounds via speakers or headphone sets, for example.
Acoustic upright pianos have strings and dampers for stopping vibrations of strings, wherein dampers are normally forced to come into contact with strings by damper springs. When keys are depressed, dampers are moved to depart from strings against forces of damper springs. In contrast, electronic upright pianos do not have strings and dampers. Even in acoustic upright pianos, no damper is arranged for each of keys of a prescribed range of pitches, for example, each of twenty keys counted from the rightmost key having the highest pitch. Therefore, acoustic upright pianos contain keys associated with dampers and other keys that are not associated with dampers, wherein key-touch feelings may differ based on their actions as to whether or not dampers are arranged therefor.
FIG. 12 shows variations of key-touch feelings that depend upon whether or not dampers are arranged therefor. In a graph of FIG. 12, the horizontal axis represents distance (in units of millimeters) by which each key is depressed, and the vertical axis represents a force (or a weight in units of grams) required for depressing each key. Herein, a curve A represents variations of force required for depressing each of keys associated with dampers, and a dotted line B represents a certain level of force required for depressing each of keys not associated with dampers (e.g., a force required for depressing a specific key not associated with a damper in an acoustic upright piano, or a force required for depressing each of keys of an electronic upright piano).
That is, each of keys not associated with dampers can be depressed with substantially a certain level of force except an initial state thereof in depression, which is shown by the dotted line B in FIG. 12. In contrast, as shown in the curve A in FIG. 12, each of keys associated with dampers must be increased in depressing force particularly in the middle of a stroke in depression and then be decreased, which indicates a so-called escapement where a load of a hammer is not applied on the keys.
When a player (or a user) depresses a key associated with a damper with a finger in an acoustic upright piano, a certain key-touch feeling is applied to a finger. In contrast, an electronic upright piano does not contain dampers, therefore, a player (or a user) cannot enjoy feeling such key-touch feelings. Even in an acoustic upright piano in which keys of higher pitches are not associated with dampers, the player (or user) cannot experience key-touch feelings similar to those produced when depressing other keys associated with dampers.